Test instruments used to measure the behavior of signals in electrical systems must be calibrated in order to gather accurate measurements. For signal processing, a typical measurement apparatus is made up of a scope, a probe module, and a probe tip. Calibration of this apparatus is accomplished by characterizing the each of these individual components and the interfaces between them. These components and their interfaces are mathematically modeled as elements of an electrical network.
Characterization requires that measurements of these components be traceable to known calibration standards. Commercially available calibration kits contain several standards for a given connector and the type of the networks to be measured. However, calibration kits are not commercially available for every connector type.
Components emerging onto the market might not be measurable using standard calibration techniques because their connector types are unsupported. Calibration kits necessary to support these connector types do not exist commercially. Measurements taken with unsupported connectors are not traceable to known calibration standards, which makes them difficult to characterize.
U.S. Pat. No. 6,823,276, issued to Blackham, et al., discloses a system and method for determining measurement errors of a testing device. A vector network analyzer (VNA) is used to measure the three systematic errors related to one-port calibration: directivity, reflection tracking, and source match. Even though standards for these three types of systematic errors are known, they may not be suitable over the entire frequency range of interest. Blackham, thus, assigns weights to standards that are more trustworthy in a particular range of frequency. These weights are applied to a least-squares calculation, resulting in a characterization of an element in a network.
U.S. Pat. No. 6,650,123, issued to Martens, discloses methods for determining characteristics of interface devices used with vector network analyzers. Martens treats a multi-port adapter or test fixture as one entity, rather than as multiple two-port networks treated one two-port network at a time. Two calibrations are performed, one at an inner reflection plane and one at an outer reflection plane.
Accordingly, there is need for a system and method that allows an operator of a signal measurement instrument to characterize and calibrate a network with unsupported connector types, not traceable to known calibration standards.